In recent years, electronic equipment such as computers, mobile phones, tablet PCs (personal computers), PDAs (personal digital assistants) and so on have become mainstream and now also include touch panels as input devices for manipulating the electronic equipment through the touch of a finger. Mutual capacitance type touch panels are developed for these types of devices.
A mobile phone ceases to detect whether or not a touch panel is touched when a user puts his/her ear to the mobile phone for calling. In this case, the contact of his/or her head to the touch panel of the mobile phone will not be detected as the action of touching the touch panel. In addition, when the user puts his/her ear to the mobile phone for calling, a display of the mobile phone is turned off in order to save power. Such type of a mobile phone has an optical proximity sensor disposed at a position corresponding to the head of the user when calling. The proximity sensor includes a pair of a light emitting device and a light receiving device. The light receiving device detects light emitted from the light emitting device and reflected by a detection target such as a user's head.
However, the use of the optical proximity sensors increases the number of components and production costs of the mobile phone. In addition, a light passage needs to be provided in the housing of the mobile phone, which restricts the design of the mobile phone.